A conventional sensor element is described in, for example, German Patent Application No. 42 31 966 (corresponding to U.S. Pat. No. 5,529,677), which is made of a composite of individual foils arranged in consecutively superimposed layers. Function layers such as electrodes, printed conductors and an electric resistance heating element are arranged between the individual foils. The function layers and the heating element are printed onto the unsintered (green) foils using screen printing, for example. Then, the foils are placed one on top of the other, laminated and subsequently sintered. In the planar sensor element of this type, the resistance heating element is arranged in one of the layers between an external cover foil and an adjacent layer structure. The resistance heating element is embedded between two electrically insulating layers (e.g., Al2O3), so that the heating conductor is electrically insulated from the adjacent foils. On its side opposite a side of the cover foil, the layer structure has a considerably greater thickness than the cover foil adjacent to the other side. Due to this highly asymmetrical arrangement of the heating element with respect to the layer sequence of the layer structure, the cover foil heats up much more than the layer structure provided with function layers. The non-homogeneous distribution of the heating power results in increased heat shock sensitivity of the planar sensor element when the temperature varies.